This prevents the glob from returning paths that don't include the root
template dir due to resolution of relative paths like `./foo`,
preventing #1541 from reoccurring. Furthermore, this prevents
misconfigured, non-existent template directories from silently passing
through, instead causing an error at init-time.
Prior to this commit, the conversion 'T -> Option<T>' was applied in
both the path and query parts of a URI in the 'uri' macro via the
'FromUriParam' trait with no implementation for 'Option<T>' directly.
This meant that it was impossible to directly render an 'Option<T>'.
This was exactly desired for the path part, where rendering a 'None'
would yield an incorrect URI, but the restriction was too strict for the
query part, where a 'None' is entirely valid. This commit makes changes
the conversion so that it only applied to path parts and adds the
identity conversions for 'Option<T>' and 'Result<T, E>' for query parts.
The side effect is a breaking change: due to conflicting impls, the 'T'
to 'Option<T>' conversion was removed for query parts. Thus, all 'uri!'
query route arguments of type 'Option' or 'Result' must now be wrapped
in 'Some' or 'Ok'. Due to new 'Option<T> <-> Result<T, E>' conversions,
either 'Some' _and_ 'Ok' work in both contexts.
Closes#1420.
Every code example is now fully runnable and testable. As a result, all
examples are now tested and include imports. Relevant imports are shown
by default. Code examples can be expanded to show all imports.
Fixes#432.
