Adding project command for GDB.

[palikar]

When I am working on a big project and I have opened a file, deep into the directory structure, it's annoying to navigate the GDB execution to the build folder. (Lots of ../../). With the new function in this, GDB can be executed at the root of the project which allows an intuitive path for the build folder to be given.

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• The commits are consistent with our contribution guidelines
• You've added tests (if possible) to cover your change(s)
• All tests are passing (make test)
• The new code is not generating bytecode or M-x checkdoc warnings
• You've updated the changelog (if adding/changing user-visible functionality)
• You've updated the readme (if adding/changing user-visible functionality)

[bbatsov]

The addition is fine by me. It needs an entry in the changelog and potentially in the docs.

[palikar]

I update the changelog but I couldn't fine a place in the docs with a big listing of all interactive commands in projectile.

[bbatsov]

Hmm, I thought we had this somewhere. Anyways, not a big deal.