Check input file version

[enzet]

If the first line of input file look like # iconscript <major>.<minor>.<patch> (minor and patch are optional), we should check the version. E.g. if line is # iconscript 0.3, version 0.3.1 is OK, and version 0.2.0 is not OK. If first line doesn't contain version pattern, we should proceed as normal.