Adding dynamic block value support in PPS

This will add the block reward typw to PPS systems. Prior to this, each
PPS value was hard coded to 50. Not only are other coins not based on
this but changing it would require code. Changed it that

* Default for fixed type is config reward
* Default for block type is **previous** blocks amount
** Fallback for first round is the fixed reward value

See in-line documentation of dist configuration. This should help new
pool owners to get setup and clarify things.

Fixes #308
Adding shares archive table back in for hash calcs

If the shares archive table is used via config option, those shares are
included when calculating the users hashrate. This will help on very
short rounds where each round end deletes all shares and users will not
be able to track their hashrates. They will be very jumpy and change to
0 all the time.

Still missing this implementation for the hourly hashrate function to
ensure the graphs are always kept up-to-date.

Addresses #331
Fixing PHP warnings on account workers page

* Fixes PHP Warning if no workers are updated
* Fixes PHP Warning in worker class if data is empty

Fixes #339
removing error reporting for debugging
Merge pull request #343 from TheSerapher/issue-339

Fixing PHP warnings on account workers page
Re-adding default My Account link

Fixes #338
Merge pull request #344 from TheSerapher/issue-338

Re-adding default My Account link
Do not use link difficulty if chaininfo unset

Fixes #336
Merge pull request #345 from TheSerapher/issue-336

Do not use link difficulty if chaininfo unset
fixing low confirmations limit in dist config
enable memcache by default
Remove link on mobile if chaininfo empty

* Remove URL from Difficulty on stats page if chaininfo is empty
* Added note to global dist configuration file

Fixes #336
Fix PHP warning in notification class

* Fix PHP Warning if no notification settings exist yet

Fixes #346
Remove PHP Warnings from worker page

* Added HTML5 required flags for username/passwords
* Added empty string check in addWorker method

Fixes #347
Merge pull request #349 from TheSerapher/issue-347

Remove PHP Warnings from worker page
Fix PHP Warnings on Password Reset page

* Added HTML5 required to username field
* Added empty string check to resetPassword method

Fixes #348
Merge pull request #350 from TheSerapher/issue-348

Fix PHP Warnings on Password Reset page
Merge pull request #351 from TheSerapher/issue-346

Fix PHP warning in notification class
Update POOLS.md

Added additional pools
Skip bogus upstream shares

This will fix an issue with blocks being assigned upstream shares that
are marked as valid but are not the actual solution for a block.

Only shares inserted when or after the block timestamp are now looked
at. This will ensure other shares inserted earlier and marked as
upstream valid are skipped.

This will not fix edge cases where many shares are inserted at the same
time and are all in the same timeframe of the block. Then the first
valid share in that time is used.

This worked fine on a testnet with a number of blocks found and false
shares inserted by hand.

Fixes #352