Forward arguments from FormatBase::operator() to emit_argument()
Remove argument error action on escaping open brackets
Ignore *.svg files in format headers directory

SVG files are generated from ragel state machines and they are very
useful in the development.
Initial fmt::Format implementation with testing application.

fmt::Format is currently writes all its output to stdout.
Fix argument indexing

Argument indexing begins from 1, so when we access array we need to
subtract 1 from it.
Throw exception when mixing indexed/non-indexed arguments placeholders
Move temporary data to stack
Move mark and capture_integer methods to FormatBase
Remove some formatting flags
Add align left flag, because it isn't default for integers
std::forward requires utility header