Use file based schema and named args for SqlContext main

[juripetersen]

Changes proposed in this PR allow named arguments for executable main function in SqlContext.java:

./bin/wayang-submit org.apache.wayang.api.sql.context.SqlContext -p java,spark,postgres -jdbcDriver org.postgresql.Driver -jdbcUrl jdbc:postgresql://job:5432/job -jdbcPassword postgres -o /var/www/html/data/benchmarks/ -d /var/www/html/data/ -q /var/www/html/data/test.sql -c file:///var/www/html/conf/wayang-defaults.properties -s file:///var/www/html/wayang-api/wayang-api-sql/src/main/resources/model.json

[chrisdutz]

Why was this change done on the protected branch?

[zkaoudi]

which protected branch?

[chrisdutz]

Please ignore my mumbling 😁