bme280 driver in Lua+C

[vsky279]

Fixes #3126, #3124, #2241,

• This PR is for the dev branch rather than for master.
• This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• I have thoroughly tested my contribution.
• The code changes are reflected in the documentation at docs/*.

Rewritten BME280 driver based on the discussion in #3126.
I intend to add also SPI support (#2527) which should be also relatively small modification of the Lua driver.

There is a conflict when original BME280 module is included in the build. require('bme280') references to the original C module and not to the new Lua driver. This can be a bit confusing. The natural solution would be to that this driver replaces the original C driver.

I assume this should be probably merged only when #3128 is implemented.

Please review the proposed commit.

[vsky279]

I don't know how to make Travis CI happy when it complains that
lua_modules/bme280/bme280.lua:22:3: accessing undefined variable bme280_math
bme280_math is the new module so it should be known to the builder.

[galjonsfigur]

@vsky279 You have to add entities in luacheck config file that can be found in tools/luacheck_config.lua. You can write it yourself or use luacheck config helper(also in tools folder) script that will generate this for you - little note on how to use it can be found here.

I thought that I've written documentation on how to add new entities in luacheck config when adding new C module but turns out I was wrong - I could add this in documentation or in project wiki.

[vsky279]

@galjonsfigur Thanks. I did manual update and now it's green.

[vsky279]

Lua 5.3 compatibility issue - lua_pushfstring works differently for non-printable characters

I was using lua_pushfstring with %c formating string to return string array of configuration parameters (3 bytes). Since Lua 5.3 the string pushed to stack for e.g. value 240 is <\240>. Different approach using just lua_pushstring is needed.

I am not sure if this cannot cause some issues in other modules.

nodemcu-firmware/app/lua53/lobject.c

Line 426 in 8d091c4

luaO_pushfstring(L, "<\\%d>", cast_uchar(buff));

[nwf]

Right! Yes, sorry to have forgotten about this one. I think it's worth landing and beginning to point people at it even if we don't yet quite have the one-shot "here's your firmware with both C and Lua modules in LFS baked in" story worked out in detail. (That depends on #3272 and probably #3138, and so probably won't be ready by next release, just given everyone's schedules, which is a little sad, but so it goes.)

Some minor changes requested.