Add team lock option to upgrades

Adds a new "smrpg_upgrade_teamlock" convar for all upgrades which lets
admins restrict access to an upgrade to a single team only.
Update team lock documentation
Translate teamlocked message in menu
Added convars to control display of locked upgrades

smrpg_show_upgrades_teamlock, smrpg_buy_upgrades_teamlock and
smrpg_show_teamlock_notice_own_team were added to control how teamlocked
upgrades are handled and displayed in the rpgmenu.
Show teamlock in admin player upgrades menu
Merge pull request #3 from peace-maker/teamlock

Add team lock option to upgrades