Fix acceleration and feedrate following bq/Marlin

[silvio-didonna]

Following bq/Marlin@8a3a270 commit.
In addition they didn't define PREFER_MAX_FEEDRATE that set:
#define DEFAULT_MAX_FEEDRATE {200, 200, 3.3, 25} // (mm/sec)
instead of defaults:
#define DEFAULT_MAX_FEEDRATE {85, 85, 3.3, 25} // (mm/sec)

I use the first because the last is really restrictive. But tell me what do you think.
However I've the hephestos and 85mm/s is A LOT for this printer. I currently print at max 60mm/s.

[thinkyhead]

I tend to agree. I hear a lot of bragging about 100mm/s feedrates (mostly on delta machines) but in practice, I've never gone much above 60mm/s, and then only experimentally. When running at such high feedrates, I find it helps to drop acceleration at the same time.

Anyway, I don't think anyone will be "disappointed" by these settings.