Handle the psdk-use studio command #15 #16

[NuriYuri]

Implements the psdk-use studio command. Fix #15 Fix #16

Test to perform:

1. In a project with no pokemonsdk folder and with no .git: psdk-use studio => Should succeed (even if it does nothing)
2. In a project with a pokemonsdk folder and with no .git: psdk-use studio => Should succeed and rename to pokemonsdk_old
3. In the same as step 2: psdk-use studio => Should fail because of pokemonsdk_old
4. In a project with a pokemonsdk submodule: psdk-use studio => Should succeed
5. In a project with a pokemonsdk submodule: psdk-use studio --delete => Should fail
6. In a project without a pokemonsdk submodule: psdk-use studio --delete => Should succeed