Fixing PHP Warning on admin->user panel

This fixes #383
Merge pull request #390 from TheSerapher/issue-383

Fixing PHP Warning on admin->user panel
Hard coded block limit for pool statistics

This should fix a potential DoS like attack when fetching a random
amount of blocks continously.

Fixes #387
Merge pull request #391 from TheSerapher/issue-387

Hard coded block limit for pool statistics
Enforce unique account emails

* display an error if user tries to re-use an email address
* moved SQL files to indicate the order of SQL import
* added unique email index SQL file

This will address #389, still needs email validation.
Fixing PHP warning message for empty price var

Fixes #375
More descriptive error message exceeding LTC threshold

Fixes #388
Fixing issue with delayed inserts for shares

When shares are inserted with a delay for performance optimizations,
this will cause block timestamps to be completely off with share
timestamps. Hence the timestamp limited search is now removed, it would
cause too many issues for Stratum users/pools.

Addresses #392
Merge pull request #393 from TheSerapher/issue-392

Fixing issue with delayed inserts for shares
Abort payout process if `share_id` is missing

If we have a block with NO `share_id` we abort the entire process. Less
of an issue with proportional since PPS is still being paid out, but a
block round will never actually end.

This will allow for manual intervention by the user. Otherwise blocks
found after the one having issues might trigger the payout process and
pay out shares of the old block in a more recently found one.

Please use #392 for further help on this, I have yet to replicate the
unknown block finder issue with the proper amount of upstream shares.
Merge pull request #394 from TheSerapher/issue-392-abort-payout

Abort payout process if `share_id` is missing
Merge pull request #395 from TheSerapher/issue-389

Enforce unique account emails

Fixes #389
Merge pull request #396 from TheSerapher/issue-375

Fixing PHP warning message for empty price var
Merge pull request #397 from TheSerapher/issue-388

More descriptive error message exceeding LTC threshold
Revert "Fixing issue with delayed inserts for shares"

This reverts commit 752b3e810fa9687e964122d602d2291123b3640a.
Improved cron logging via logfiles

* Added 3rd party logger library KLogger
* Adjusted all cronjobs from verbose output to logging
* Added new logs folder for crons to write to
* Added new .gitignore for logs folder data
* Updated blocks class to only fetch blocks with no share_id
* Adjusted findblocks to use no blocks class method
Fallback call if upstream share not found properly

Implemented a fallback method in case no upstream share can be found for
a block. This will result in same strange behaviour especially if a
later block has properly added a valid share and this will be used for a
previous block. At least now even the last block will be properly found
and marked as discovered by a user, even though no actual upstream share
was involved in this.

This is a dirty workaround for pools having payout issues. After all
blocks are processed and assuming upstream shares continue to work as
expected, this will *skip* broken blocks/shares.

Workaround fix for #392
Merge remote-tracking branch 'upstream/issue-392' into vardiff-pushpool-compatibility