(#24): drop tables before restore

* added Db.TryExecute method (Db.execute now throws exception by
default)
* adapted Install to use TryExecute and Config to use execute
move the db version getter into config
display db version of the backup

+ notify about required upgrade after backup restore
fix session start in upgrade (#29)

the session is not started so the flashbag does not work and
the upgrade result is never displayed

introduced by fac0f40b96e682a1d478bee575d2bdad60399393
added comment support
fixed some style
added an Html::Encode function
use Html::Encode to encode comment
removed style on comment text box
changed text
delete the info file linked with the backup
Merge branch 'db_backup_info' (fix #33)
(#8)use Html::Encode to encode html
fix #34 typo in text
allow up to 32000 chars over 4 lines
fix the js text limiting function
changed ades_faits.motif capacity
Merge branch 'increase_motif_size' fix #32