Countries v2.1.0

Additions

added Czech translations
added Polish translations
added missing Croatian translation for Sint Maarten

Fixes

replaced "Northern America" by "North America"
removed fund codes from currencies
renamed Swaziland to Eswatini
revised some German translations
fixed Vatican City demonym
fixed Macau demonym
fixed some Unicode typos
fixed type of 'name.native' when property is empty
fixed official and common country name of Korea
fixed official and native name of the Netherlands (#277)

Build

fixed output message when converting with specific format(s) (#281)
formatted code to comply with PSR2 coding standard
removed Hungarian notation in PHP Code
moved dependency roave/security-advisories to require-dev section

Miscellaneous

added badge for PHP minimum version
added scrutinizer badge