Real literals

Added support for:

1. Parsing decimal and double real literals (e.g. 1.2, 1.2, 32.2e+3, 1.4d)
2. Real literal addition
3. Numeric multipliers (e.g. kb, mb, gb, tb)
4. Addition involving hex numbers in double quotes (e.g. 1.2 + "0xabc")

Some real literals are not supported by Pash but work with PowerShell:

    1.
    3.e3
    32.e+12