Support for gatewayaccesstoken

[jurepurgar]

Description

Resolves #2461.

Motivation and Context

Support for RD gateways with pluggable authentication

How Has This Been Tested?

Tried to connect from mRemote via RD gateway configured with pluggable authentication. The RDP connection was successful.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Changed feature (non-breaking change which changes functionality)
• Changed feature (breaking change which changes functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Updated translation

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• All Tests within VisualStudio are passing
• This pull request does not target the master branch.
• I have updated the changelog file accordingly, if necessary.
• I have updated the documentation accordingly, if necessary.

[jurepurgar]

@Kvarkas I'm first time contributor to his project so I'm not familiar with the codebase. Is this everything that is needed to add a new connection property?

[Kvarkas]

@Kvarkas I'm first time contributor to his project so I'm not familiar with the codebase. Is this everything that is needed to add a new connection property?

it may need update schema but I could do it, will try to merge to test at evenining.