Added Ability to Disable JMC in Visual Studio

[nickclark2016]

What does this PR do?

This PR resolves #1526. It adds a "jmc" option to projects in order to disable just my code debugging.

Usage:

project "SomeProject"
   justmycode "Off"

How does this PR change Premake's behavior?

There is no change for preexisting projects, thus it is a non-breaking change. By settings justmycode to "Off" in a VS2017 or newer project, it adds a flag to the project file to disable JMC.

Anything else we should know?

N/A

Did you check all the boxes?

• Focus on a single fix or feature; remove any unrelated formatting or code changes
• Add unit tests showing fix or feature works; all tests pass
• Mention any related issues (put closes #XXXX in comment to auto-close issue when PR is merged)
• Follow our coding conventions
• Minimize the number of commits

[starkos]

Thanks for this, and all the help you've been providing lately—much appreciated!

[nickclark2016]

Just to follow up on this, can we get a justmycode page in the wiki? And no problem! I try to contribute back changes that I've used in my own projects as well as help pick up some of the low hanging fruit.

[smbradley]

Shouldn't this be a boolean? It seems kind of weird to be able to set it to Off but not to On