added nvarchar data type to definitions, added additional model/file generation options, updated README

[sequ3l]

changes:

• added nvarchar data type to definitions for microsoft sql server and other dialects.
• added additional options for model generation.
• updated README
• convert dir/typeDir to posix path in writeFile()
• allow dir/typeDir as absolute windows path in writeFile()

options:

• noModelSuffix: removes the "Model" or "_model" suffix added to model names. default is false.
• fileNameMatchesModel: write the file with the same name as the model. default is false.
• sequelizeNamespace: specify a custom sequelize namespace that will be used during model generation instead of requiring sequelize, e.g. 'app.sequelize'. default is empty string.
• templatePath: specify a path to a custom template for model generation. default uses sequelize-automate template depending on 'type'.

[aoi-umi]

option fileNameMatchesModel but fileNameMatchModel in util/definition.js

function getModelDefinitions(tables, options) {
  const { sequelizeNamespace, camelCase, noModelSuffix, fileNameCamelCase, fileNameMatchModel, dialect, } = options || {};