GH-23 Fix issue where stale dependency cache could be used across builds

[romeara]

Change caching logic for loaded dependency information to include time
modified, to prevent stale cached content from being used when changes
are made between builds. This situation could arise due to the Gradle
Daemon re-using class loaders between builds

[codecov]

Codecov Report

Merging #25 into master will decrease coverage by 0.37%.
The diff coverage is 80%.

@@             Coverage Diff              @@
##             master      #25      +/-   ##
============================================
- Coverage     85.04%   84.67%   -0.38%     
+ Complexity      252      251       -1     
============================================
  Files            25       25              
  Lines           749      757       +8     
  Branches         53       53              
============================================
+ Hits            637      641       +4     
- Misses           91       93       +2     
- Partials         21       23       +2

Impacted Files	Coverage Δ	Complexity Δ
...abs/flare/plugins/model/DependencyConstraints.java	86.11% <80%> (-6.75%)	10 <3> (ø)
...rchartlabs/flare/plugins/model/ConstraintFile.java	96.15% <0%> (-3.85%)	12% <0%> (-1%)

[blackduck-copilot]

Black Duck Security Report

Merging #25 into master will not change security risk.

Click here to see full report

[nickavv]

sad that this is required but good solution

[romeara]

Yeah, am displeased with Gradle for necessitating it, but didn't want to reload dependencies in every project