Limited loading of OpenSCAD files

Removed print statement + clear model list when loading file (probably should add a dirty flag as well to avoid accidentally overriding changes)

Print time guesstimation on file load

Added OBJ to the types of files that can be opened.

Added final semicolon after final OBJ in the file filter

Proposed changes in the MacosX pre lion installation instructions

Second try - Proposed changes in the MacosX pre lion installation instructions as per irc conversation.

improve french translation.

Cleaned up commit from l4nce0

    Now when the program starts the last temp is set for Heater and Bed. Also a (user) is attached if it is a manual entry.

last used serial port pre-selection logic change, based on if it is autodetected to be present or not