ImplementA Hack 5.0 + Redeem Codes

optimizing for iPad: just tap once to select item of todo list
优化对Ipad的支持：解决在todo中选择习题时需要点击两次的问题

multiplication formula, equation,equations,inequality,inequalities,fractionEquation. and get value with relative knowledge.
乘法公式,方程,方程组,不等式,不等式组,分式方程. 及利用相关知识求值.
本版本不支持Ipad

1.add integral and fraction
2.use point to express multiplication in relative operation
3.use correct parenthesis () [] {} at relative position of expression
4.erase bugs of v2
1.新增整式与分式
2.在相关运算中用点表示乘法
3.在相关位置正确使用 () [] {}
4.清楚版本V2中的bug

1.support 0 index of exponentiation, such as 2^(4-4),a^(2x-2x)
2.display (x^2)^(2m-3n) correctly
3.report invalid when user input (0),(3) in expression, such as 2(0),4(1)
4.support factoring for 9-4,4-12+9 by completeSquere or SqureDifference
5.support 1^x,1^5,that base nummber equal 1 for exponentiation
6.support sin 1,cos 2....
7. support factoring for 2^2-2*2*3+3^2
8.eliminate several bug which cause exit app when jump between the detail page of how and todo