Add basic validation to set password screen

Fixes #78
Improve name validation

Insist on a space somewhere in the name to match server side rules.
Fixes #76
Display reposition report button after recentering map

If recentering the map moves the crosshair position to somewhere
different to the current report location then display the reposition
button. Includes small margin of error for GPS noise etc.
Fixes #75
Merge remote-tracking branch 'origin/master'