Fixed emitter erroring out

Caused by Emitter:Finish being fixed in GMod update, but removing the
emitter too early caused it to error. Emitter now removed on aircraft
removal.
Merge pull request #102 from weltensturm/emitter-fix

Fixed emitter erroring
Fixed reference to wire base entity

Fixes #98
Merge pull request #103 from weltensturm/wirebaseent-fix

Fixed reference to wire base entity
Merge branch 'master' into dev
Made arcade mode easier