Support for custom headers downloading files

[ewilde]

Resubmitting pull request from: chocolatey-archive/chocolatey#171
Implements issue: #246

Some web sites require specific headers to allow you to download the
setup program/zip

functions:
Get-WebFile.ps1
Get-ChocolateyWebFile.ps1
Install-ChocolateyPackage.ps1
Install-ChocolateyZipPackage.ps1

now support an options hashtable which allows use to specify individual
headers.

The options hash table structure allows for future settings to be flowed through the application without updating multiple method signatures.

The structure at the moment is:

 
$options = @ {
   Headers = @{
      Header1 = 'somevalue'; Header2 = 'somevalue'
 }
}

In the future you could use the options to pass down cookies by domain for example

 
$options = @ {
   Headers = @{
      Header1 = 'somevalue'; Header2 = 'somevalue'
   };
   Cookies = @{
      'http://domain.com' = 'value1';
      'http://secure.domain.com = 'value2';
   }   
}

[ferventcoder]

@ewilde This is close to what I was thinking, but @patrickmaurer was taking your changes and applying them here, so he didn't feel comfortable signing the CLA. For this to move forward he would have to sign the CLA because of the way you've resubmitted this. I would prefer the commits be from you and the commit messages be appropriate to a github issue. Can you make those changes?

[ewilde]

@ferventcoder sure thing I'll create a new issue and PR