[IMPROVED] Allow for longer monitoring value strings
[ADDED] Error Code Array
[IMRPOVED] Error Notification Mail with new headers
[IMPROVED] Re-factored monitoring criticals/errors

* [ADDED] new monitoring method : endCronjob
* [IMPROVED] Use newly added error codes
* [ADDED] mail notifications, enabled by default
* [ADDED] cron disable on fatal errors with exit code != 0
* [ADDED] Command line swtich: -f = Force running crons even if disabled
* [ADDED] Disabled status in monitoring site

This will improve error handling in our cronjobs. Fatal errors now
require manual intervention by explicityly running crons with the force
option (`-f`). Until they are forced to run, crons will stay disabled.

Fixes #773 once merged
[FIX] Disable mail notifications on disabled crons
[IMPROVED] Added logging failed SQL queries to payouts
[FIX] Double error message in log
[IMPROVED] More testing of error handling, block class
[REFACTOR] Refactored classes for error handling

* [ADDED] More error codes
* [MODIFIED] Class updates to use Base Class all the time
* [MODIFIED] Cronjobs have been slightly adjusted
* [ADDED] More base class features
[FIX] Removed empty error string
[FIX] Do not use Block Height to fetch prev block

This should fix issues with orhpan blocks followed by real ones with the
same height.

Fixes #715, attempt four!
[FIX] Settings return value on empty result
[IMPROVED] Block statistics

* [ADDED] Block over times stats to blocks stats page
* [CHANGED] Split default block stats page template up into subtemplates
* [IMPROVED] Single SQL Query for all Block Stats over Time
* [UPDATED] Templates for new SQL Data
[FIX] Surpress PHP notices on empty registration vars
Merge pull request #817 from TheSerapher/issue-773

Issue 773
Merge pull request #828 from TheSerapher/optimize-blockstats

[IMPROVED] Block statistics
[FEATURE] calculating-luck
[FIX] division by zero
[FEATURE] added block finding rate - HINT new config setting cointarget
[UPDATE] removed unused stuff