Change gulpfile.js file to support multiple solution files in root folder

[Antonytm]

If you have few solution files in source folder, you will get error: 'MSBUILD : error MSB1050: Specify which project or solution file to use because the folder "..............." contains more than one project or solution file.' when running 'Publish-All-Projects' task.

It will be good, if you can add few solution files in root folder, but still be able to use gulp build.

It is some kind of bug, but you need to modify your source that is why I have created it as feature.

Steps to reproduce:

1. Copy Habitat.sln to Habitat1.sln
2. Run 'Publish-All-Projects' task
   Expected result: 'Publish-All-Projects' task should succeed
   Actual result: error: 'MSBUILD : error MSB1050: Specify which project or solution file to use because the folder "..........." contains more than one project or solution file.'

[Antonytm]

Done in PR #487