Update JavaMail dependency to 1.6.2, adding support for authenticated HTTP web proxy

[bbottema]

In JavaMail 1.6.0 HTTP proxy support was added and in 1.6.2 authentication was added as well. Simple Java Mail should support this in the builder API as well.

JavaMail has moved btw:
Project home: https://eclipse-ee4j.github.io/javamail/
Code home: https://github.com/eclipse-ee4j/javamail

The following properties are concerned:

property	type	description
mail.smtp.proxy.host	string	Specifies the host name of an HTTP web proxy server that will be used for connections to the mail server.
mail.smtp.proxy.port	string	Specifies the port number for the HTTP web proxy server. Defaults to port 80.
mail.smtp.proxy.user	string	Specifies the user name to use to authenticate with the HTTP web proxy server. By default, no authentication is done.
mail.smtp.proxy.password	string	Specifies the password to use to authenticate with the HTTP web proxy server. By default, no authentication is done.

SOCKS authentication is still not supported by JavaMail, so Simple Java Mail's SOCKS (v5) authentication is still relevant.

[Flashky]

Oh god, I need this so much 👍

Thank you for your efforts!
Besides this, I have a question about license, if I'm my project I'm using your SimpleJavaMail library, do I have to mention the license? or just if I modify it?

At least, for now I mention you on my README.md to give you credit for this awesome library. :)

[bbottema]

Hi @Flashky, please refer to https://tldrlegal.com/license/apache-license-2.0-(apache-2.0) on the right side under Must.

[bbottema]

Updated javax.mail version for upcoming release 6.0.0.