Parser upgrade; introducing ECGP

[subbyte]

Prepare for v1.5.0. Details in CHANGELOG.rst.

[codecov[bot]]

Codecov Report

Base: 80.92% // Head: 82.31% // Increases project coverage by +1.39% :tada:

Coverage data is based on head (e1d57bd) compared to base (976daec). Patch coverage: 88.58% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #253      +/-   ##
===========================================
+ Coverage    80.92%   82.31%   +1.39%     
===========================================
  Files           39       41       +2     
  Lines         2506     2703     +197     
===========================================
+ Hits          2028     2225     +197     
  Misses         478      478              

Impacted Files	Coverage Δ
src/kestrel/analytics/interface.py	80.00% <ø> (ø)
src/kestrel/codegen/summary.py	98.07% <ø> (ø)
src/kestrel_analytics_docker/interface.py	20.98% <ø> (+0.74%)	:arrow_up:
src/kestrel/symboltable/symtable.py	71.42% <71.42%> (ø)
src/kestrel/syntax/reference.py	78.26% <78.26%> (ø)
src/kestrel/syntax/ecgpattern.py	79.16% <79.16%> (ø)
src/kestrel/exceptions.py	65.81% <80.00%> (-0.26%)	:arrow_down:
src/kestrel/semantics/reference.py	87.17% <87.17%> (ø)
src/kestrel/codegen/relations.py	71.72% <88.88%> (+0.29%)	:arrow_up:
src/kestrel/semantics/processor.py	91.46% <91.46%> (ø)
... and 13 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[pcoccoli]

This PR is too big to review properly.