[Done] Global shift add-ons

[daniel]

Highlighting the ' significant digits' is a very good idea. And I'll also indicate that the local coordinates are the ones CC is working with (CC doesn't store anything on disk by default).

For the first loaded cloud the suggested shift is deduced from the very first point of the file (so as to apply the shift right from the first point in order to avoid losing any information). 'Bookmarks' are also checked and if one works it will be suggested by default. For the next files the same happen, but before checking the bookmarks, we check the previous input first. So if the user works only within the same geographical area, only one shift vector should be suggested by CC (by default).

And for the bookmark file, it was suggested by Dimitri only for people who are always working on the same datasets / areas (and also for tutorial classes for instance I believe).

[daniel]

Hum, not very easy to mix the characters color in a Qt label... I switched to an adaptive precision (i.e. the user sees only the significant digits).