[BUGFIX] Use ctype_digit instead of is_numeric

The is_numeric function returns TRUE on fx string "z123" which ctype_digit does not - it's preferable to return FALSE on strings like this.
[BUGFIX] Use PREG_SET_ORDER on preg_match_all

This causes the $matches array to be filled in a way which allows the subsequent conditions to function properly when $global = TRUE.
[BUGFIX] Abstract Iterator returns FALSE if item is in position zero

Casting to boolean replaced with check for strict FALSE !==.
[BUGFIX] Single Math ViewHelpers used incorrect value when $a is Iterator
[BUGFIX] Multiple Math ViewHelpers used incorrect value when $a is Iterator
[BUGFIX] Multiple Math ViewHelpers performed Iterator access check on non-Iterators
[BUGFIX] Math / Median uses incorrect slicing point and midpoint calculation
[BUGFIX] Ensure consistent return type in Math / Range ViewHelper
[BUGFIX] Var / Convert used incorrect ObjectStorage check and conversion
[TASK] Various cleanups and optimisations without changing any behavior
[TASK] Massive cleanup and improvement to tests in multiple namespaces
Merge pull request #333 from NamelessCoder/cleaning

[TASK] Numerous bugfixes, cleanups and test improvements