Adds onPaste validation, fix adds with decimal and toPresicion bug

[nachodd]

• Adds onPaste handler that check if the actual value pasted is a valid Numeric value.
• Corrects a bug when adding or subtracting numbers with decimals.
• Fix toPresicion fn bug: If the initial value is an integer, it fails to apply toFixed

[nachodd]

I've also created another validations, like disabling the "e" to be entered (as input type number supports scientific notation, but is rarely used). If you want, I can create another PR.