translation: combine old and current wikis

translation: combine old and current wikis

This takes all of the relevant information from
an old wiki site (https://pve.proxmox.com/wiki/Translations)
and merges it into the document that is used in generating the
admin guide and current wiki
(https://pve.proxmox.com/wiki/Translating_Proxmox_VE) entry.

Also contains some rewording for better readability.

V2: - Broke up into multiple sections for further clarity
      - Separate sections for translating with and without git.
      - Separate section for various methods of testing the
	translation
      - Separate section for various methods of submitting the
	translation
    - Incorporate suggested changes from previous version

Signed-off-by: Dylan Whyte <d.whyte@proxmox.com>