Created %cvt:defvar function, removed from main processing flow, for use
in get-template-vars and %cvt:with.
Added 'format' attribute handling for cvt:var + uri-encoding format.
Added tests for cvt:with, cvt:interpolate, and cvt:macro.
1) Added standard-test-context function 2) Reorganized test groups
3) Added tests for cvt:interpolate and cvt:macro.
Implemented cvt:interpolate.
Corrected some apparently wrong SXPath expressions.
Added get-template-macros function.
Added log-var function for debugging.
Fixed a few minor bugs.