[TESTS] refactor tests and add g_gear to the cvar that are expected to respond at plugin startup
[4.2][!gear] allow weapon aliases as parameter of the !gear command

To ease the !gear command usability, weapon/item keys alias can be defined.
For instance, one could type `!gear +de` while someone else could type `!gear +desert` to allow the _Desert Eagle_.

Also:
  - add tests for the 4.2 specific !gear implementation
  - Update doc by adding a 4.2 specific doc section for the !gear command
Merge pull request #2 from thomasleveil/#17

fix tests regarding changes for #17 and introduce weapon/item aliases