Improve version specific executable searching.

[EtorixDev]

I was having some issues testing v1 behavior while working on another pull request because the library couldn't find my v1 installation. I completely uninstalled AutoHotkey twice and tested two install configurations to see how it behaved and rewrote the executable searching code to accommodate it.

The first time I installed v1 then v2. In this case, v1 installed into C:\Program Files\AutoHotkey and v2 installed into C:\Program Files\AutoHotkey\v2.

The second time I installed v2 then v1 (how I originally had it installed). In this case, v2 installed into C:\Program Files\AutoHotkey\v2 and v1 installed into C:\Program Files\AutoHotkey\v1.1.37.02.

So the rewritten code will search the top level install directory if v1 is selected, otherwise it will search for v1... or v2... directories and then search there.

I put all of the executables in a single list to save a line and an if statement but can split it if necessary.

EXECUTABLES = ['AutoHotkey.exe', 'AutoHotkey64.exe', 'AutoHotkey32.exe', 'AutoHotkeyU64.exe', 'AutoHotkeyU32.exe', 'AutoHotkeyA32.exe']
# vs
V2_EXECUTABLES = ['AutoHotkey.exe', 'AutoHotkey64.exe', 'AutoHotkey32.exe']
V1_EXECUTABLES = ['AutoHotkey.exe', 'AutoHotkeyU64.exe', 'AutoHotkeyU32.exe', 'AutoHotkeyA32.exe']