Add conditions

[kcasctiv]

Simple functionality for conditions. Something similar to ranges. Actually here introduced block concept. Both ranges and conditions now just different types of blocks.

Each block begins with {{blockName fieldName}} and ends with {{end}}.

So there is no changes for ranges.

Conditions begin with {{if cond}}. Also there is {{else}} for false conditions.

Simple example

	A	B
1	{{if fieldA}}
2		{{fieldA}}
3	{{else}}
4		{{fieldB}}
5	{{end}}