add Smarty template tokenizer

[glensc]

asked Smarty own parser/tokenizer to parse .tpl files: smarty-php/smarty#364
no replies so far, so wrote my own.

• parse .tpl into token stream
• extract line number context
• process token list into usable object

NOTE: this requires that all block functions be available when template is parsed. for initial release {t} block handler is present via composer dependency.

[glensc]

known issue: line number context is not known

EDIT: fixed