Enables parenthesis evaluation.

Conflicts:
	source/blocks.js
Fixed parentheses multiplication/blank issues.
Fixes double negative issue.

Conflicts:
	source/blocks.js
Small fix to a rebase incorrect edit.
Fixes more issues caused when rebasing
More equation handling changes made.
Fixes issue when x proceeds a number and assigns multiplication operator.
Changed + and - returns to strings.
Final fixes
Merge pull request #218 from virtual-world-framework/graph-parentheses

Enables parenthesis evaluation