Upgrade to clara 0.18.0, use rule builder, fix missing listener method

[alex-dixon]

#115

• Upgrade to clara 0.18.0
• Add empty fire-activations! to listeners to satisfy new protocol
• Use clara.rules.dsl/build-rule in CLJ rule macro code paths
• Add mk-session to create anonymous sessions in Clojure

[codecov]

Codecov Report

Merging #116 into master will decrease coverage by 0.03%.
The diff coverage is 54.16%.

@@            Coverage Diff             @@
##           master     #116      +/-   ##
==========================================
- Coverage   56.82%   56.79%   -0.04%     
==========================================
  Files          23       23              
  Lines        1714     1722       +8     
  Branches      114      107       -7     
==========================================
+ Hits          974      978       +4     
- Misses        626      637      +11     
+ Partials      114      107       -7

Impacted Files	Coverage Δ
src/cljc/precept/listeners.cljc	50.38% <ø> (ø)	⬆️
src/cljc/precept/rules.cljc	65.25% <54.16%> (-7.48%)	⬇️
src/cljc/precept/query.cljc	80% <0%> (+15%)	⬆️
src/cljc/precept/impl/rules.cljc	100% <0%> (+44.44%)	⬆️

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