[Input] added support for limiting the maximum number of values and groups at input

Bug fix: yes
Feature addition: yes
Backwards compatibility break: no
Tests pass: yes
Fixes the following tickets: #7 
Todo: Update documentation.
License of the code: MIT

The defaults are set at: 100 values per field per group, and 30 groups allowing 3000 values in total.
This is a good default and will prevent DoS attacks by setting a large number of values.