There are newer pandas versions which still support python2. The latest
one which still supports py2 (0.24.x) has initially been released in 2019
and should therefore be quite stable and better supported. We should
therefore prepare ERP5 so that it support those newer versions.

This patch mostly fixes movements within the internal pandas structure.
The patch still supports old object locations of previous pandas versions.

/reviewed-on !1738
/reviewed-by @jerome @klaus