Detect frontend directory locations dynamically based on project

[mstahv]

If source and target directories are not explicitly defined, those are now detected dynamically based on the project type, so that spring boot projects don't need special settings.

This change is 

[caalador]

Review status: 0 of 2 files reviewed at latest revision, all discussions resolved.

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flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/maven/CopyProductionFilesMojo.java, line 64 at r1 (raw file):

        if(frontendWorkingDirectory == null) {
            // No directory given, try to find from common locations
            for(String dir : Arrays.asList(

Break out arrays.asList to have the for more readable.

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flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/maven/PackageForProductionMojo.java, line 117 at r1 (raw file):

                    && project.getArtifactMap().containsKey("com.vaadin:vaadin-spring-boot-starter")) {
                // in spring boot project there is not web app directory
                transpileOutputDirectory = new File(project.getBuild().getDirectory(), "classes/META-INF/resources");

drop "classes" and use getOutputDirectory() instead of getDirectory()

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Comments from Reviewable

[caalador]

Review status: 0 of 2 files reviewed at latest revision, 2 unresolved discussions.

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flow-maven-plugin/src/main/java/com/vaadin/flow/plugin/maven/CopyProductionFilesMojo.java, line 68 at r1 (raw file):

                    "src/main/resources/META-INF/resources/frontend", 
                    "src/main/resources/public/frontend",
                    "src/main/resources/static/frontend")) {

missing "src/main/resources/resources/frontend"

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Comments from Reviewable

[caalador]

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Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[mstahv]

@ripla, we need probably some similar logic to Designer, so that it creates design files to src/main/resources/META-INF/frontend for spring boot projects. Shall I create an issue for that?