All config variables starts with low-case and uses camelCase.
If there is abbreviation at the beginning of the name, the whole
abbreviation will be written in low-case.
If there is abbreviation at the end of the name, the
whole abbreviation will be written in upper-case.
For example, rssURI.
The gain, given the "real sites benchmark" below, is obvious:
```
benchmark old ns/op new ns/op delta
BenchmarkHugo-4 14497594101 13084156335 -9.75%
benchmark old allocs new allocs delta
BenchmarkHugo-4 57404335 48282002 -15.89%
benchmark old bytes new bytes delta
BenchmarkHugo-4 9933505624 9721984424 -2.13%
```
Fixes#2495
