Operator brackets ([]) implemented in CL backend via fetch-property.

It allows the use expressions like "$myvar['myproperty']" instead of
"$myvar.myproperty".
Merge branch 'master' of github.com:archimag/cl-closure-template
Revert "fix indentation in closure-template-html-mode"

This reverts commit bfeda732b3293d0e4c76dafaa141c06adf8ece92.
Improved closure-template-html-mode
Add custom directive support to RequireJS backend

Additional parameter is added REGISTER-PRINT-HANDLER - :MODULE.
It is usefull when actual function implementation is loaded via RequireJS
too and contains URI for module containing functin :FUNCTION.
As javascript backend, implementation can be specified via :HANDLER argument.
To handle directive parameters :PARAMETER-CONVERTER must be used.
Merge remote branch 'archimag/master' into print-directives