feat(IMOS): metadata extraction queries

Includes some repeatable patterns of query/meta data access.

`IMOS.meta.beam_face_config` - discover the beam face config of an ADCP.
`IMOS.meta.site_bathymetry` - discover the local bathymetry.
`IMOS.meta.velocity_variables` - discover all velocity variables in a
dataset.

Util/+IMOS/+meta/beam_face_config.m

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+function [beam_face_config] = beam_face_config(sample_data)
+% function [beam_face_config] = beam_face_config(sample_data)
+%
+% Get the beam face config of an ADCP.
+%
+% Inputs:
+%
+% sample_data [struct] - the toolbox dataset.
+%
+% Outputs:
+%
+% beam_face_config [char] - 'up','down' or empty.
+%
+% Example:
+%
+% %basic usage
+%
+%
+% author: hugo.oliveira@utas.edu.au
+%
+try
+    beam_face_config = sample_data.meta.adcp_info.beam_face_config;
+	return
+catch
+	try
+		bin_dist = IMOS.get_data(sample_data.dimensions,'HEIGHT_ABOVE_SENSOR');
+	catch
+		try
+			bin_dist = IMOS.get_data(sample_data.dimensions,'DIST_ALONG_BEAMS');
+		catch
+			beam_face_config = '';
+			return
+		end
+	end
+    if all(bin_dist>0)
+        beam_face_config = 'up';
+    elseif all(bin_dist<0)
+        beam_face_config = 'down';
+    else
+        beam_face_config = '';
+    end
+end
+
+end

Util/+IMOS/+meta/site_bathymetry.m

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+function [depth] = site_bathymetry(sample_data, oper)
+%function [depth] = site_bathymetry(sample_data, oper)
+%
+% Disambiguate the site bathymetry from a sample
+%
+% Inputs:
+%
+% sample_data [struct] - the toolbox struct
+% oper [function handle] - a function handle to operate on
+%                         the different estimates if any.
+%                         Default: @min
+%
+% Outputs:
+%
+% depth [numeric] - the bathymetry value
+%
+%
+% Example:
+% sample_data.site_nominal_depth = [];
+% sample_data.site_depth_at_deployment = [];
+% assert(isempty(IMOS.meta.get_site_bathymetry(sample_data)))
+% sample_data.site_nominal_depth = 20;
+% assert(IMOS.meta.get_site_bathymetry(sample_data)==20)
+% sample_data.site_depth_at_deployment = 10;
+% assert(IMOS.meta.get_site_bathymetry(sample_data)==10)
+%
+% author: hugo.oliveira@utas.edu.au
+%
+%
+narginchk(1, 2)
+
+if ~isstruct(sample_data)
+    errormsg('Not a struct')
+end
+
+if nargin == 1
+    oper = @min;
+else
+
+    if ~isfunctionhandle(oper)
+        errormsg('Second argument not a function handle')
+    end
+
+end
+
+try
+    b1 = sample_data.site_depth_at_deployment;
+catch
+    b1 = [];
+end
+
+try
+    b2 = sample_data.site_nominal_depth;
+catch
+    b2 = [];
+end
+
+if isempty(b1)
+    b1 = b2;
+end
+
+if isempty(b2)
+    b2 = b1;
+end
+
+depth = oper(b1, b2);
+
+end

Util/+IMOS/+meta/velocity_variables.m

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+function [vnames] = velocity_variables(sample_data)
+% function [vnames] = velocity_variables(sample_data)
+%
+% Get the velocity variable names (UCUR,VCUR,and variants)
+% from a dataset.
+%
+% Inputs:
+%
+% sample_data [struct] - the toolbox dataset.
+%
+% Outputs:
+%
+% vnames [cell{str}] - A cell with velocity variable names.
+%
+% Example:
+%
+% %basic usage
+% dims = IMOS.gen_dimensions('adcp');
+% vars = IMOS.gen_variables(dims,{'VEL1','VEL2','UCUR','VCUR'});
+% x.variables = vars;
+% vnames = IMOS.meta.velocity_variables(x);
+% assert(isempty(setdiff(vnames,{'UCUR','VCUR','VEL1','VEL2'})));
+% x.variables = IMOS.gen_variables(dims,{'UCUR_MAG','VCUR_MAG','WCUR'});
+% vnames = IMOS.meta.velocity_variables(x);
+% assert(isempty(setdiff(vnames,{'UCUR_MAG','VCUR_MAG','WCUR'})));
+%
+% % ambiguity is not handled.
+% x.variables = IMOS.gen_variables(dims,{'UCUR','UCUR_MAG'});
+% vnames = IMOS.meta.velocity_variables(x);
+% assert(isempty(setdiff(vnames,{'UCUR','UCUR_MAG'})))
+%
+%
+% author: hugo.oliveira@utas.edu.au
+%
+narginchk(1,1);
+try
+	varcell = sample_data.variables;
+catch
+	errormsg('No variable fieldname available.')
+end
+avail_variables = IMOS.get(varcell,'name');
+allowed_variables = {'UCUR_MAG','UCUR','VCUR_MAG','VCUR','WCUR','WCUR_2','ECUR','VEL1','VEL2','VEL3','VEL4'};
+vnames=cell(1,numel(allowed_variables));
+c=0;
+for k= 1:numel(avail_variables)
+	vname = avail_variables{k};
+	if inCell(allowed_variables,vname)
+		c=c+1;
+		vnames{c} = vname;
+	end
+end
+vnames=vnames(1:c);
+end