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
Potential fix for PHP Warning

This should fix #327
Fixing PHP Warnings in Registration page

* Fix API Key generation not using SALT when creating hash
 * This should not affect existing API keys since hashes are compared
* Fix PHP Warning for RECAPTCHA if disabled

Fixes #328
Merge pull request #333 from TheSerapher/issue-328

Fixing PHP Warnings in Registration page
Merge pull request #334 from TheSerapher/issue-327

Potential fix for PHP Warning
Starting to add pools to README/POOLS file
Update POOLS.md
Show nethash rate in MHash/s not GHash/s

* Easier to compare directly with pool hashrate
* Better display format for low nethash rate coins

Fixes #331
Merge pull request #335 from TheSerapher/issue-331

Show nethash rate in MHash/s not GHash/s
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
Merge pull request #340 from TheSerapher/issue-303

Issue 303
Fixing strict PHP warnings when registering a user

Fixes #329
Merge pull request #342 from TheSerapher/issue-329

Fixing strict PHP warnings when registering a user
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