All interface methods implemented, parameters now handled
Switched to using BigInteger where possible to handle exceeding the double limitations.
Adds "from" and "to" values, incrementer values, "about" window and help screen.
Merge branch 'master' into jake/GUI

Conflicts:
	MathsThing_GUI/src/uk/ac/uea/mathsthing/gui/GUI.java
Removes incrementer option, fixes up the UI a bit.
Switched parser to use Token types rather than Strings.
Merge branches 'LauraLexer' and 'jordan/parser' into LauraLexer

Conflicts:
	MathsThing_GUI/src/uk/ac/uea/mathsthing/Lexer.java
Fixed the parser to allow it to build evaluation trees with functions embedded.
lexer updated to use enums, interface and tests upfated to reflect change
Merge branch 'jordan/parser' into LauraLexer
Fixed the pattern matching being in the wrong order.
fixed lexer regex once more to handle functions properly.