Skip Hidden and System migration files by default

[wite27]

Hi! I faced an issue when using Evolve in Kubernetes with mounting migration scripts as volumes via ConfigMap. To make long story short, in that case Kubernetes creates hidden folder ..data with files from ConfigMap at mountPath, and creates symlinks to mounted files, i.e.

Sql_Scripts
├── R__migration.sql --> links to ..data/R__migration.sql
├── ..data (hidden)
│   └── R__migration.sql --> links to ..2020_03_03_16_40_36.675612011/R__migration.sql
├── ..2020_03_03_16_40_36.675612011 (hidden)
│   └── R__migration.sql

And because Evolve does not skip Hidden files, it crashes with Found multiple sql migration files with the same version: R__migration.sql.

Also, that behavior is similar with Flyway, which skips hidden files by default.

Tip: I could use GetFiles with EnumerationOptions overload, but it's not supported in netstandard2.0

[wite27]

@lecaillon could you take a look, please?

[lecaillon]

Will release an Evolve 3.1.0-alpha7 next week.