site: added 1e-12 numerical tolerance for site eq
site: added 1e-12 numerical tolerance for site eq

Site's _eq__() is now a bit more robust and handles float precision
comparisons better, with 1e-12 absolute tolerance.

mmpagani/oq-hazardlib,g-weatherill/oq-hazardlib,gem/oq-engine,vup1120/oq-hazardlib,rcgee/oq-hazardlib,rcgee/oq-hazardlib,ROB-Seismology/oq-hazardlib,ROB-Seismology/oq-hazardlib,gem/oq-hazardlib,mmpagani/oq-hazardlib,gem/oq-engine,silviacanessa/oq-hazardlib,larsbutler/oq-hazardlib,silviacanessa/oq-hazardlib,gem/oq-engine,g-weatherill/oq-hazardlib,silviacanessa/oq-hazardlib,gem/oq-engine,g-weatherill/oq-hazardlib,gem/oq-engine,mmpagani/oq-hazardlib,larsbutler/oq-hazardlib,ROB-Seismology/oq-hazardlib,g-weatherill/oq-hazardlib,larsbutler/oq-hazardlib,vup1120/oq-hazardlib,silviacanessa/oq-hazardlib,ROB-Seismology/oq-hazardlib,gem/oq-hazardlib,gem/oq-hazardlib,vup1120/oq-hazardlib