Support MaxPool layer before conv->fc flatten

Install XRT from .deb

Fixes #341

Remove close-to-identity ops

Upgrade Brevitas to get bias export fixes

Conv->FC transition w/ spatial dim != (1,1)

all heavier builds moving to finn-examples

Merge branch 'feature/nhwc_flatten' of https://github.com/fpjentzsch/finn into fpjentzsch-feature/nhwc_flatten

can be customized via env.var

Meta-PR for 1D-as-non-square ops and finn-base updates

Merge branch 'feature/1d_convolution_support' of https://github.com/mmrahorovic/finn into feature/1d_convs_and_finn_base_update

Merge branch 'feature/convolutioninputgenerator_nonsquare' of https://github.com/mmrahorovic/finn into feature/1d_convs_and_finn_base_update