Fixed bug which led to empty ath9k crontab file

The crontab file was opened in write mode but in the case where no monitor is defined it would leave an empty file.
Merge pull request #46 from lcb01a/master

Fixed bug which led to empty ath9k-workaround crontab file
ecdsautils: update to v0.3.2
gluon-autoupdater: add version_file option to uci settings
autoupdater: convert to Lua

In addition, a new config field 'version_file' is added to remove the last
Gluon-specific part from the autoupdater package.
autoupdater: add a utility function to parse RFC3339 timestamps
autoupdater: implement new probablity logic
gluon-autoupdater: adjust for new updater logic

The probability field is removed, updates are performed once per night between
04:00 and 05:00.
autoupdater: add -o (oneshot) switch

This switch is used for the fallback mode which ensures that updates are
performed even when a node is off when updates are usually done.
gluon-autoupdater: add locking to ensure no two instances of the autoupdater run in parallel
gluon-autoupdater: unconditionally perform an update 5 minutes after boot when the whole PRIORITY delay has passed