Make ethlo excludable

[justin-tay]

Closes #973

This makes the ethlo dependency excludable. This isn't the same as making it optional as optional dependencies need to be explicitly added, while excludable needs to be explicitly excluded.

[codecov-commenter]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (bc93b44) 78.75% compared to head (0519d3f) 78.63%.

Files	Patch %	Lines
...va/com/networknt/schema/format/DateTimeFormat.java	43.75%	7 Missing and 2 partials ⚠️
.../main/java/com/networknt/schema/utils/Classes.java	40.00%	3 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff              @@
##             master     #974      +/-   ##
============================================
- Coverage     78.75%   78.63%   -0.12%     
- Complexity     1850     1851       +1     
============================================
  Files           164      165       +1     
  Lines          5987     6001      +14     
  Branches       1146     1147       +1     
============================================
+ Hits           4715     4719       +4     
- Misses          837      846       +9     
- Partials        435      436       +1     

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